Semiconductor device and manufacturing method thereof

ABSTRACT

A semiconductor device of the present invention is furnished with (a) a first protection film, formed on a substrate, having an opening section on an electrode pad, (b) a protrusion electrode, connected on the electrode pad at the opening section, whose peripheral portion is formed to overlap the first protection film, (c) a second protection film, formed to cover at least a gap at a boundary portion of the first protection film and the protrusion electrode, having an opening on a top area of the protrusion electrode except a portion around the boundary portion of the first protection film and the protrusion electrode, and (d) a coating layer formed to cover a surface of the protrusion electrode at the opening of the second protection film. With this arrangement, it is possible to provide a semiconductor device wherein the protrusion electrode is formed with an electroless plating method, capable of preventing the lowering of the adhesion strength of the protrusion electrode to the electrode pad.

FIELD OF THE INVENTION

The present invention relates to a semiconductor device having aprotrusion electrode for external connection of an electrode pad, and amanufacturing method thereof; and in particular relates to asemiconductor device wherein the protrusion electrode is formed with anelectroless plating method, and a manufacturing method thereof.

BACKGROUND OF THE INVENTION

As a mounting technique for mounting a semiconductor device on anothersemiconductor device, a printed board, a tape carrier, etc., there is atechnique for forming a protrusion electrode for external connection onan electrode pad of the semiconductor device. One of the methods offorming the protrusion electrode is to use an electroless plating methodfor forming the protrusion electrode on the electrode pad composed ormainly composed of Al.

Compared to an electrolytic plating method, the electroless platingmethod can eliminate steps such as a sputtering process required forforming a barrier metal layer and for forming an electrode in a platingprocess, a photo process required for forming a pattern of theprotrusion electrode, and an etching process required for removing aresist used in the pattern forming process and for removing the barriermetal used in the plating process. As described above, the electrolessplating method has beneficial features in reducing cost and inquickening the time of delivery.

However, the conventional arrangement for forming the protrusionelectrode using the electroless plating method causes a problem in theadhesion strength of the protrusion electrode to the electrode pad. Forexplaining this problem, the following will explain steps for formingthe protrusion electrode on the electrode pad composed of Al or alloymainly composed of Al (Al alloy) using the electroless plating method,with reference to FIGS. 9( a) through 9(e).

FIG. 9( a) shows a semiconductor device before the protrusion electrodeis formed. An electrode pad 102 composed of Al or Al alloy is formed ona semiconductor substrate 101. On the electrode pad 102, a firstprotection film 103 is further formed so as to have an opening where theprotrusion electrode is to be formed. Oxide film 104 exists over asurface of the electrode pad 102 where the first protection film 103 hasthe opening portion.

In a step shown in FIG. 9( b), the oxide film 104 over the surface ofthe electrode pad 102 is completely removed with sodium hydroxide,phosphoric acid, etc. The oxide film 104 is removed in a followingreason. Namely, if the oxide film 104 exists over the surface of theelectrode pad 102, a shape and reliability of the protrusion electrodeare significantly affected while the protrusion electrode is formed onthe electrode pad 102 using the electroless plating method. Thus, in theelectroless plating method, the oxide film 104 is removed from thesurface of the electrode pad 102 with sodium hydroxide or phosphoricacid as pre-treatment of plating, thereby ameliorating the shape of theprotrusion electrode formed with Ni or Ni alloy.

FIG. 9( c) shows a zincate treatment, which is a pre-treatment processfor depositing Ni or Ni alloy as the protrusion electrode on theelectrode pad 102 using the electroless plating method. In the zincatetreatment, the displacement reaction between Zn and Al or Al alloycomposing the electrode pad 102 is uniformly carried out, therebyforming a Zn layer 105 on the surface of the electrode pad 102.

In a step shown in FIG. 9( d), a protrusion electrode 106 composed of Nior Ni alloy is formed on the electrode pad 102 using the electrolessplating method. In this step, a layer of Ni or Ni alloy as a core isfirst formed through displacement reaction with respect to Zn, and thenthe protrusion electrode 106 is formed through autocatalytic reaction.Thus, by uniformly forming Zn grains, the protrusion electrode formedwith Ni or Ni alloy plating uniformly grows. As a result, the protrusionelectrode 106 can be obtained in a small grain size and in a good shape.

As shown in FIG. 9( e), an Au layer 108 is formed on the protrusionelectrode 106 composed of Ni or Ni alloy, in a displacement Au platingprocess. The Au layer 108 may achieve an effect of preventing theoxidation of Ni or Ni alloy composing the protrusion electrode 106.

In the step shown in FIG. 9( d), the protrusion electrode 106, which isformed through the autocatalytic reaction of Ni or Ni alloy, is alsoformed on the first protection film 103. At a boundary portion of thefirst protection film 103 and the protrusion electrode 106, however, aminute gap 107 remains without chemically bonded.

In the displacement Au plating process shown in FIG. 9( e), displacementAu plating liquid enters the minute gap 107 between the first protectionfilm 103 and the protrusion electrode 106. Further, the displacement Auplating liquid entered into the gap 107 carries out incompletedisplacement reaction between Ni and Au because the liquid is notsufficiently replaced. This causes a phenomenon that only Ni dissolves.Consequently, as shown in FIG. 9( e), the protrusion electrode 106 isthinned down at the opening portion of the first protection film 103,thereby significantly lowering the adhesion strength of the protrusionelectrode 106 to the electrode pad 102.

SUMMARY OF THE INVENTION

In order to solve the foregoing problems, the object of the presentinvention is to provide a semiconductor device wherein a protrusionelectrode is formed with an electroless plating method, capable ofpreventing the lowering of the adhesion strength of the protrusionelectrode to an electrode pad, and a manufacturing method thereof.

In order to attain the foregoing object, a semiconductor device of thepresent invention is characterized by including (a) a first protectionfilm, formed on a semiconductor substrate, having an opening section onan electrode pad, (b) a protrusion electrode, connected on the electrodepad at the opening section, whose peripheral portion is formed tooverlap the first protection film, (c) a second protection film, formedto cover at least a gap at a boundary portion of the first protectionfilm and the protrusion electrode, having an opening on a top area ofthe protrusion electrode except a portion around the boundary portion ofthe first protection film and the protrusion electrode, and (d) acoating layer formed to cover a surface of the protrusion electrode atthe opening of the second protection film.

With this arrangement, the second protection film coats the gapgenerated between the first protection film and the protrusion electrodewhen the protrusion electrode is formed on the first protection film.With this, in a process for forming the coating layer which is formed tocover the protrusion electrode at the opening of the second protectionfilm (usually a displacement Au plating process), it is possible toprevent the problems such that the displacement Au plating liquidentered the gap dissolves the metal that forms the protrusion electrodeso as to lower the adhesion strength of the first protection film to theprotrusion electrode.

In order to attain the foregoing object, a manufacturing method of asemiconductor device of the present invention, wherein a firstprotection film is formed on a semiconductor substrate expect at aportion on an electrode pad, and a protrusion electrode whose surface iscoated with a coating layer is further formed on the electrode pad, ischaracterized by including the steps of (A) forming a protrusionelectrode on the electrode pad with electroless plating, (B) forming asecond protection film, so as to cover at least a gap at a boundaryportion of the first protection film and the protrusion electrode,having an opening on an top area of the protrusion electrode except aportion around the boundary portion of the first protection film and theprotrusion electrode, and (C) forming the coating layer for coating thesurface of the protrusion electrode at the opening of the secondprotection film.

With this method, the protrusion electrode is formed on the electrodepad using the electroless plating in the step (A). Here, the protrusionelectrode is formed to be higher than the first protection film, but theperipheral portion of the protrusion electrode is formed to overlap thefirst protection film. Further, since the protrusion electrode and thefirst protection film are not chemically bonded where the protrusionelectrode overlaps the first protection film, a gap is generated betweenthe first protection film and the protrusion electrode.

Next, the second protection film is formed in the step (B). The secondprotection film has the opening on almost an entire top area of theprotrusion electrode except at the portion around the boundary portionof the first protection film and the protrusion electrode, so as toreveal the head of the protrusion electrode. In other words, the secondprotection film, which is formed in the step (B), coats the gapgenerated between the first protection film and the protrusionelectrode.

Then, in the step (C), the coating layer for coating the surface of theprotrusion electrode is formed with the displacement Au plating. Here,the gap generated between the first protection film and the protrusionelectrode is coated with the second protection film.

Consequently, in the step (C), it is possible to prevent problems suchthat the displacement Au plating liquid entered the gap between thefirst protection film and the protrusion electrode dissolves the metalthat forms the protrusion electrode so as to lower the adhesion strengthof the first protection film to the protrusion electrode.

For a fuller understanding of the nature and advantages of theinvention, reference should be made to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing an arrangement of a semiconductordevice, and shows an embodiment of the present invention.

FIGS. 2( a) through 2(d) are sectional views showing a part of steps ina manufacturing method of the semiconductor device.

FIGS. 3( a) through 3(c) are sectional views showing a part of steps inthe manufacturing method of the semiconductor device.

FIGS. 4( a) through 4(e) are sectional views showing an example of stepsfor forming an opening at a second protection film in the manufacturingmethod of the semiconductor device.

FIGS. 5( a) and 5(b) are sectional views showing an example of steps forforming an opening at a second protection film in the manufacturingmethod of the semiconductor device.

FIGS. 6( a) and 6(b) are sectional views showing an example of steps forforming an opening at a second protection film in the manufacturingmethod of the semiconductor device.

FIG. 7 is a sectional view showing an example where the semiconductordevice of the present invention is mounted on another device usinganisotropic conductive film.

FIG. 8 is a sectional view showing an example where a solder bump isformed on a protrusion electrode of the semiconductor device of thepresent invention.

FIGS. 9( a) through 9(e) are sectional views showing steps of amanufacturing method of a conventional semiconductor device.

DESCRIPTION OF THE EMBODIMENTS

The following will explain an embodiment of the present invention withreference to FIGS. 1 through 8.

FIG. 1 shows an arrangement of a semiconductor device in accordance withthe present embodiment.

As shown in FIG. 1, the semiconductor device is composed in a mannersuch that an active element (not shown) and wiring, etc., are formed ona substrate (semiconductor substrate) 1. An electrode pad 2 is formed asa part of the wiring. The electrode pad 2 is formed with Al or Al alloy,for example.

Note that, though a Si wafer is widely used as the substrate 1, thematerial of the substrate 1 is not particularly limited in the presentinvention, and may be appropriately selected in accordance with theusage of the semiconductor device.

Further, on the active element and the wiring, a first protection film 3is formed for protection. Note that, the first protection film 3 has anopening section on the electrode pad 2, and a protrusion electrode 4 isformed on the electrode pad 2 at the opening section. The protrusionelectrode 4 is formed with Ni or Ni alloy, for example.

On the first protection film 3 and the protrusion electrode 4, a secondprotection film 5 is formed. The second protection film 5 is providedfor preventing plating liquid from entering a gap between the firstprotection film 3 and the protrusion electrode 4 during a step offorming a coating layer 6 as later described. Thus, the secondprotection film 5 is formed so as to coat at least a boundary portion ofthe first protection film 3 and the protrusion electrode 4. Further, thesecond protection film 5 has an opening portion on almost an entire toparea of the protrusion electrode 4 except at a portion around theboundary portion of the first protection film 3 and the protrusionelectrode 4.

Then, on the protrusion electrode 4, the coating layer 6 is formed atthe opening portion of the second protection film 5. The coating layer 6coats the surface of the protrusion electrode 4, for preventing theoxidation of the metal that forms the protrusion electrode 4, and forachieving effects of thermo compression bonding in connection withanother device when the semiconductor device is mounted. The coatinglayer 6 is preferably formed with Au.

Next, a method of forming the protrusion electrode in the semiconductordevice will be explained with reference to FIGS. 2( a) through 2(d), and3(a) through 3(c).

FIG. 2( a) shows the semiconductor device before the protrusionelectrode 4 is formed, wherein the first protection film 3 is formed onthe substrate 1 after the active element, the wiring, etc. are formed onthe substrate 1. The first protection film 3 has been already providedwith the opening section on the electrode pad 2. Further, oxide film 7has been already formed on the surface of the electrode pad 2. In somecases, fluoride has been formed in accordance with fluorine gas used foretching the first protection film 3 (for forming the opening on theelectrode pad 2).

If the protrusion electrode 4 is formed when the oxide film 7 is formedon the surface of the electrode pad 2, the shape and reliability of theprotrusion electrode 4 are greatly affected, as has been described inthe background art. For removing the oxide film 7 (or the fluoride), theetching is carried out on the electrode pad 2 with sodium hydroxide orphosphoric acid, for example, before the protrusion electrode 4 isformed. FIG. 2( b) shows the semiconductor device in which the oxidefilm 7 (or the fluoride) is removed by the etching.

After the oxide film 7 is removed, a Zn layer 8 is formed with adisplacement plating method as a further pre-treatment process, beforethe protrusion electrode 4 is formed on the surface of the electrode pad2. FIG. 2( c) shows a state wherein the displacement reaction between Znand Al on the surface of the electrode pad 2 is uniformly carried out onthe electrode pad 2.

The Zn layer 8 is formed in a manner such that sequential steps of (1)immersing the semiconductor device of FIG. 2( b) into an alkalinesolution including Zn, (2) rinsing the semiconductor device withpurified water, and (3) immersing the semiconductor device into nitricacid, are carried out about once or twice, and then the step (1) iscarried out again.

Thus, the semiconductor device is immersed into the alkaline solutionincluding Zn at least twice, and, in this case, the electrode pad 2composed of Al or Al alloy is etched for approximately 400 nm with thealkaline solution. Consequently, in the previous step of etching theelectrode pad 2 for removing the oxide film 7, the electrode pad 2 mustretain a thickness of at least 500 nm after the etching. If the Al layerthat forms the electrode pad 2 is lost in the step of forming the Znlayer 8, the protrusion electrode 4 loses its adhesion strength, therebycausing the lowering of the reliability of the semiconductor device whenmounted.

Further, in the step of FIG. 2( c), Pd may be deposited on the surfaceof the electrode pad 2 through Pd catalytic activation instead of thedisplacement reaction of Zn. The Pd catalytic activation processdisplaces Al for an amount smaller than that displaced in thedisplacement reaction of Zn, thus resulting in a smaller etched amountof the Al layer that forms the electrode pad 2.

FIG. 2( d) shows a state wherein the protrusion electrode 4 is formed onthe electrode pad 2. In this step, the protrusion electrode 4 is formedby immersing the semiconductor device of FIG. 2( c) into acidic solutionincluding Ni and a reductant of Ni, in a process such that Ni layer isformed on the elctrrode pad 2 through the displacement reaction betweenZn and Ni or Ni alloy, and then Ni or Ni alloy is deposited throughautocatalytic reaction. Here, since Zn grains are uniformly deposited inthe Zn layer 8, the displacement reaction between Zn and Ni as well asthe autocatalytic reaction of Ni are uniformly carried out, therebyforming the protrusion electrode 4 in a good shape.

Here, the protrusion electrode 4 is formed to be higher than the firstprotection film 3, in consideration of obtaining a space on a mountingsurface when the semiconductor device is mounted on another device. Theprotrusion electrode 4 here is only required to have a height H ofapproximately 5 μm. By forming the protrusion electrode 4 higher thanthe first protection film 3 as described above, a peripheral portion ofthe protrusion electrode 4 is formed to overlap the first protectionfilm 3, as shown in FIG. 2( d).

Note that, the protrusion electrode 4 which is generally composed of Nior Ni alloy is not chemically bonded with the first protection film 3which is generally composed of inorganic film or resin. This generates aminute gap 9 between the first protection film 3 and the protrusionelectrode 4 (namely, at the boundary portion of the first protectionfilm 3 and the protrusion electrode 4).

FIG. 3( a) shows a state wherein the second protection film 5 is formedon the semiconductor device of FIG. 2( d) on a side where the protrusionelectrode 4 is formed. The second protection film 5 may be inorganicinsulation film or organic insulation film, but FIG. 3( a) shows a casewhere the second protection film 5 is formed with the organic insulationfilm, as an example.

When the second protection film 5 is formed with the inorganicinsulation film (SiN, SiO₂, SiO, SiON, etc.), SiN film or SiO₂ film isformed so as to have a thickness of no less than 500 nm, using a P-CVD(Plasma Chemical Vapor Deposition) method, etc., for example. Further,when the second protection film 5 is formed with the organic insulationfilm (PI, BCB, etc.), polyimide resin, etc. may be applied so as to belower than the protrusion electrode 4, using a spin coat method, etc.,for example.

The second protection film 5 is provided with an opening portion on theprotrusion electrode 4 in an area smaller than the protrusion electrode4, as shown in FIG. 3( b). Namely, a diameter D1 of the protrusionelectrode 4 is larger than a diameter D2 of the opening portion. Thissecond protection film 5 completely coats the gap 9 generated betweenthe first protection film 3 and the protrusion electrode 4.

Various methods can be used for forming the opening portion at thesecond protection film 5, but three methods will be explained here asexamples. First, a first method will be explained with reference toFIGS. 4( a) through 4(e).

In this case, as shown in FIG. 4( a), a resist 10 is applied on anentire surface of the second protection film 5 in the semiconductordevice of FIG. 3( a). Then, as shown in FIG. 4( b), the resist 10 isexposed via a photomask 11 having an opening where the second protectionfilm 5 is to be removed.

Next, by developing the exposed resist 10, the resist 10 is removed atthe exposed area, as shown in FIG. 4( c). Further, by carrying outetching with the developed resist 10 as a mask, the second protectionfilm 5 is provided with the opening, as shown in FIG. 4( d). Then, byexfoliating the resist 10 as shown in FIG. 4( e), the semiconductordevice of FIG. 3( b) can be obtained, in which the second protectionfilm 5 has the opening at a predetermined portion.

Here, when the second protection film 5 is formed with the inorganicinsulation film such as SiN, a dry etching device is used. The dryetching can be carried out in the same condition as in a general methodof etching SiN. Here, the etching is carried out for approximately oneor two minutes in vacuum using a gas such as CF₄.

Next, a second method will be explained with reference to FIGS. 5( a)and 5(b). This method can be used when the second protection film 5 isformed with photosensitive polyimide resin, etc.

In this case, first, as shown in FIG. 5( a), the second protection film5 is directly exposed via the photomask 11 having an opening where thesecond protection film 5 is to be removed. Then, as shown in FIG. 5( b),by developing the exposed second protection film 5, the semiconductordevice of FIG. 3( b) can be obtained, in which the second protectionfilm 5 has the opening at a predetermined portion.

Last, a third method will be explained with reference to FIGS. 6( a) and6(b). With this method, the second protection film 5 is mechanicallyremoved on the protrusion electrode 4. More specifically, as shown inFIG. 6( a), the second protection film 5 is abraded until the top areaof the protrusion electrode 4 is revealed (until a dashed line in FIG.6( a)). With this, as shown in FIG. 6( b), the semiconductor device ofFIG. 3( b) can be obtained, in which the second protection film 5 hasthe opening at a predetermined portion.

After the second protection film 5 is provided with the opening at apredetermined portion as shown in FIG. 3( b), the coating layer 6 isformed at the opening portion of the second protection film 5 in a stepshown in FIG. 3( c). The top surface of the protrusion electrode 4 isthus coated with the coating layer 6, thereby completing thesemiconductor device in accordance with the present embodiment.

The coating layer 6 is preferably formed by plating Au on the protrusionelectrode 4. When formed with the Au plating, the coating layer 6 isformed using displacement Au plating, but may be further formed to havean increased thickness using electroless Au plating.

More specifically, in the displacement Au plating, the semiconductordevice of FIG. 3( b) is immersed into displacement Au plating liquid for10 through 30 minutes, so that Au is deposited for a thickness ofapproximately 0.05 μm on the surface of the protrusion electrode 4through displacement reaction between Ni and Au.

Here, the coating layer 6 formed using the Au plating is mainly providedfor preventing the oxidation of the protrusion electrode 4, as describedabove, but also for achieving effects of thermo compression bonding inthe connection with another device when the semiconductor device ismounted. When the protrusion electrode 4 of the semiconductor device isconnected to an inner lead of a TCP (Tape Carrier Package) having adevice hole, in particular, the bonding is generally carried out in amanner such that a surface of the inner lead is plated with Sn, and thenSn and Au are alloyed using thermo compression bonding.

Note that, when carrying out the bonding through Sn—Au alloying asdescribed above, the thickness of Au plating of the coating layer 6 isnot sufficient with the above-described thickness of approximately 0.05μm (approximately 0.08 μm in the maximum). In this case, the Au platinglayer as the coating layer 6 is further formed thicker using theelectroless plating. In other words, in this case, the displacement Auplating is carried out as a pre-treatment process of the electroless Auplating.

With the electroless Au plating, the Au layer further grows because theplating solution contains a redundant, thereby forming the Au layer asthe coating layer 6 to have a thickness of approximately 1 μm in theend.

In the semiconductor device manufactured with the above-describedmethod, the second protection film 5 coats the gap 9 generated betweenthe first protection film 3 and the protrusion electrode 4. Thisprevents the displacement Au plating liquid from entering the gap 9during the displacement Au plating for forming the coating layer 6. Thiscan prevent problems such that the displacement Au plating liquidentered the gap 9 dissolves Ni that forms the protrusion electrode 4 andthe protrusion electrode 4 is thinned down at the opening section of thefirst protection film 3 so as to lower the adhesion strength of theprotrusion electrode 4 to the electrode pad 2.

Next, an example of mounting the semiconductor device in accordance withthe present embodiment will be explained.

FIG. 7 shows an example of connecting the semiconductor devices witheach other. In this case, two semiconductor devices 20 and 21 areconnected using thermo compression bonding in a manner such that one ofthe semiconductors 20 and 21 is tentatively compressed with anisotripicconductive film 22 (or is applied with anisotropic conductive paste),while the other of the semiconductors 20 and 21 is aligned on that. Theanisotropic conductive film 22 is composed of conductive grains 24dispersed into insulation binder resin 23. The both protrusionelectrodes of the connected semiconductor devices 20 and 21 areconnected with each other via the conductive grains 24. The optimalcondition for the thermo compression bonding here is a temperature ofapproximately 200° C. and a pressure of approximately 1000 kg/cm².

Further, the example of connecting the semiconductor devices shown inFIG. 7 assumes a case where the coating layer for coating the protrusionelectrode is formed by using only the displacement Au plating. However,the semiconductor devices may be directly connected with each otherusing thermo compression bonding of Au—Au, provided that the Au layer asthe coating layer is formed to have the increased thickness using theelectroless Au plating or the electrolytic Au plating in at least one ofthe semiconductor devices.

Further, in addition to the case of connecting the semiconductor deviceswith each other, the above-described connecting method can be applied tocases where the semiconductor device in accordance with the presentembodiment is mounted on another printed board, TCP, COF (Chip On Film),etc. Note that, when the semiconductor device is mounted on insulationfilm such as the TCP and the COF, the insulation film having no devicehole is used.

Further, in the semiconductor device in accordance with the presentembodiment, a solder bump 25 may be formed on the protrusion electrode4, as shown in FIG. 8. The solder bump 25 can be formed in a generalmethod wherein flux is applied on the protrusion electrode 4, a solderball is mounted, and reflowing is performed. The solder bump 25 may alsobe formed using solder plating.

In a case where the solder bump 25 is formed on the protrusion electrode4, Sn enters the gap between the electrode pad 2 and the Ni protrusionelectrode 4 so as to form fragile metal alloy composed of Sn, if thesecond protection film 5 is not formed. This lowers the adhesionstrength of the protrusion electrode 4. In contrast, with thearrangement where the second protection film 5 is formed, the secondprotection film 5 prevents the entrance of Sn, thereby preventing thelowering the adhesion strength of the protrusion electrode 4.

Note that, for forming the solder bump 25, Au is required to be formedas the coating layer 6 on the protrusion electrode 4. In the arrangementof FIG. 8, the coating layer 6 is fused into the solder bump 25.

Incidentally, in the present invention, the materials of the electrodepad, the protrusion electrode, the coating layer, etc., are not limitedto those have been explained. For example, the electrode pad may beformed with Cu, etc., instead of Al or Al alloy. When the electrode padis formed with Cu, the Zn displacement reaction process shown in FIG. 2(c) will be replaced with the Pd catalytic activation process. Further,the protrusion electrode may be arranged to have Cu layer-Ni layer-Aulayer, Cu layer-Au layer, etc. on the electrode pad, instead of beingformed with the Ni layer or the Ni alloy layer as explained above.

As described above, a semiconductor device of the present invention ischaracterized by including (a) a first protection film, formed on asemiconductor substrate, having an opening section on an electrode pad,(b) a protrusion electrode, connected on the electrode pad at theopening section, whose peripheral portion is formed to overlap the firstprotection film, (c) a second protection film, formed to cover aboundary portion of the first protection film and the protrusionelectrode, having an opening on almost an entire top area of theprotrusion electrode except a portion around the boundary portion of thefirst protection film and the protrusion electrode, and (d) a coatinglayer formed to cover a surface of the protrusion electrode at theopening of the second protection film.

With this arrangement, the second protection film coats the gapgenerated between the first protection film and the protrusion electrodewhen the protrusion electrode is formed on the first protection film.With this, in a process for forming the coating layer which is formed tocover the protrusion electrode at the opening of the second protectionfilm (usually a displacement Au plating process), it is possible toprevent the problems such that the displacement Au plating liquidentered the gap dissolves the metal that forms the protrusion electrodeso as to lower the adhesion strength of the first protection film to theprotrusion electrode.

The semiconductor device of the present invention is preferably arrangedso that the protrusion electrode is formed with Ni or Ni alloy.

As in this arrangement, the protrusion electrode is beneficially formedwith Ni or Ni alloy, not only because the cost is low and thedisplacement Au plating is easily carried out, but also the hardmaterial can reduce the damage when connected to the electrode pad (ifthe protrusion electrode is made of a soft material, the electrode padspreads sideways, thereby causing a crack on a foundation of theelectrode pad).

The semiconductor device of the present invention may be so arrangedthat the second protection film is formed with inorganic insulationfilm.

With this arrangement, it is possible to achieve high reliability due tothe characteristics of the inorganic film.

The semiconductor device of the present invention may be so arrangedthat the second protection film is formed with organic insulation film.

With this arrangement, the second protection film can be formed withphotosensitive resin. This simplifies the process for forming theopening at the second protection film, thereby reducing the cost.

The semiconductor device of the present invention may be so arrangedthat a solder bump is formed on the protrusion electrode.

As in this arrangement, when the solder bump is formed on the protrusionelectrode, Sn enters the gap between the electrode pad and the Niprotrusion electrode so as to form fragile metal alloy composed of Sn,if the second protection film is not formed. This lowers the adhesionstrength of the protrusion electrode.

In contrast, with the arrangement where the second protection film isformed, the second protection film prevents the entrance of Sn, therebypreventing the lowering the adhesion strength of the protrusionelectrode. Thus, the above arrangement can preferably adopt the presentinvention.

A manufacturing method of a semiconductor device of the presentinvention, wherein a first protection film is formed on a semiconductorsubstrate expect at a portion on an electrode pad, and a protrusionelectrode whose surface is coated with a coating layer is further formedon the electrode pad, is characterized by including the steps of (1)forming a protrusion electrode on the electrode pad with electrolessplating, (2) forming a second protection film on the semiconductorsubstrate on a side where the protrusion electrode is formed, (3)forming an opening at the second protection film, on almost an entiretop area of the protrusion electrode except at a portion around aboundary portion of the first protection film and the protrusionelectrode, so as to reveal a head of the protrusion electrode, and (4)forming the coating layer for coating the surface of the protrusionelectrode at the opening of the second protection film with displacementAu plating.

With this method, the protrusion electrode is formed on the electrodepad using the electroless plating in the step (1). Here, the protrusionelectrode is formed to be higher than the first protection film, but theperipheral portion of the protrusion electrode is formed to overlap thefirst protection film. Further, since the protrusion electrode and thefirst protection film are not chemically bonded where the protrusionelectrode overlaps the first protection film, a gap is generated betweenthe first protection film and the protrusion electrode.

Next, the second protection film is formed in the step (2). In the step(3), the opening is formed at the second protection film on almost theentire top area of the protrusion electrode except at the portion aroundthe boundary portion of the first protection film and the protrusionelectrode, so as to reveal the head of the protrusion electrode. Inother words, the second protection film, which is formed in the steps(2) and (3), coats the gap generated between the first protection filmand the protrusion electrode.

Then, in the step (4), the coating layer for coating the surface of theprotrusion electrode is formed with the displacement Au plating. Here,the gap generated between the first protection film and the protrusionelectrode is coated with the second protection film.

Consequently, in the step (4), it is possible to prevent problems suchthat the displacement Au plating liquid entered the gap generatedbetween the first protection film and the protrusion electrode dissolvesthe metal that forms the protrusion electrode so as to lower theadhesion strength of the first protection film to the protrusionelectrode.

The manufacturing method of the semiconductor device of the presentinvention, wherein the step (3) of forming the opening at the secondprotection film may include the steps of (i) forming a resist on thesecond protection film, (ii) patterning the resist with aphotolithography technique, (iii) etching the second protection filmwith the patterned resist as a mask, and (iv) exfoliating the resist.

With this method, when the inorganic film, which has high reliability,is used for forming the second protection film, it is possible to formthe opening at the second protection film.

The manufacturing method of the semiconductor device of the presentinvention, wherein the step (3) of forming the opening at the secondprotection film may include the step of patterning the second protectionfilm with a photolithography technique, wherein the second protectionfilm is formed with photosensitive resin.

With this method, it is possible to eliminate steps such as applying,exposing, revealing, and exfoliating the resist, and thus the secondprotection film can be formed in simplified steps, thereby reducing thecost.

The manufacturing method of the semiconductor device of the presentinvention, wherein the step (3) of forming the opening at the secondprotection film may include the step of mechanically abrading the secondprotection film on the protrusion electrode so as to reveal the head ofthe protrusion electrode.

With this method, by mechanically abrading the top portion of theprotrusion electrode, it is possible to reduce unevenness in height ofthe protrusion electrode on a wafer surface, thereby forming the head ofthe protrusion electrode flat. This can reduce connection defects andthe like caused by the unevenness in height of the protrusion electrode,thereby widening a margin of conditions for connection.

The manufacturing method of the semiconductor device of the presentinvention, may further include the step of (5) forming the coating layerto have an increased thickness with electroless Au plating, aftercarrying out the step (4).

With this method, when the protrusion electrode of the semiconductordevice is connected to an inner lead of a TCP having a device hole, forexample, it is possible to carry out the connection by alloying Sn andAu using thermo compression bonding, after a surface of the inner leadis plated with Sn.

The manufacturing method of the semiconductor device of the presentinvention may further include the step of (6) forming a solder bump onthe protrusion electrode by mounting a solder ball on the protrusionelectrode and by performing reflowing on the solder ball, after carryingout the step (4).

The manufacturing method of the semiconductor device of the presentinvention may further include the step of (7) forming a solder bump onthe protrusion electrode with electroless solder plating, after carryingout the step (4).

As in these methods, when the solder bump is formed on the protrusionelectrode, Sn enters the gap between the electrode pad and the Niprotrusion electrode so as to form fragile metal alloy composed of Sn,if the second protection film is not formed. This lowers the adhesionstrength of the protrusion electrode.

In contrast, with the arrangement where the second protection film isformed, the second protection film prevents the entrance of Sn, therebypreventing the lowering the adhesion strength of the protrusionelectrode. Thus, the above arrangements can preferably adopt the presentinvention.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art intended tobe included within the scope of the following claims.

1. A semiconductor device, comprising: a first protection film, formedon a semiconductor substrate, the first protection film having anopening section defined therein over an electrode pad; a protrusionelectrode, connected to the electrode pad at the opening section definedin the first protection film, wherein only a peripheral portion of theprotrusion electrode is formed to overlap said first protection film sothat a majority of the protrusion electrode does not overlap the firstprotection film; a second protection film formed to cover at least a gapat a boundary portion of said first protection film and said protrusionelectrode, said second protection film having an opening defined thereinover a top area of said protrusion electrode except a portion around theboundary portion of said first protection film and said protrusionelectrode so that a majority of a top surface of the protrusionelectrode is not covered by the second protection film; a conductivecoating layer formed to cover the top surface of said protrusionelectrode at the opening of said second protection film so that amajority of the top surface of the protrusion electrode is covered bythe conductive coating layer; and wherein a top surface of theconductive layer and a top surface of the second protection film form asmooth continuous transition at an interface therebetween which islocated on a sidewall of the protrusion electrode.
 2. The semiconductordevice of claim 1, wherein said conductive coating layer is formedsubstantially conformally to the top surface of the protrusionelectrode.
 3. The semiconductor device of claim 1, wherein an upperportion of the protrusion electrode is at an elevation above a top ofthe second protection film.
 4. The semiconductor device as set forth inclaim 1, wherein: said protrusion electrode is formed with Ni or Nialloy.
 5. The semiconductor device as set forth in claim 1, wherein:said second protection film is formed with inorganic insulation film. 6.The semiconductor device as set forth in claim 1, wherein: said secondprotection film is formed with organic insulation film.
 7. Thesemiconductor device as set forth in claim 1, wherein: a solder bump isformed on said protrusion electrode.
 8. The semiconductor device ofclaim 1, wherein the only portion of the protrusion electrode that iscovered by the second protection film is an edge of the protrusionelectrode located proximate the boundary portion of the first protectionfilm.
 9. A semiconductor device, comprising: a first protection film,formed on a semiconductor substrate, the first protection film having anopening section defined therein over an electrode pad; a protrusionelectrode, connected to the electrode pad at the opening section definedin the first protection film, wherein only a peripheral portion of theprotrusion electrode is formed to overlap said first protection film sothat a majority of the protrusion electrode does not overlap the firstprotection film; a second protection film formed to cover at least a gapat a boundary portion of said first protection film and said protrusionelectrode, said second protection film having an opening defined thereinover a large portion of a top area of said protrusion electrode so thata majority of a top surface of the protrusion electrode is not coveredby the second protection film; a conductive coating layer formed tocover the top surface of said protrusion electrode at the opening ofsaid second protection film so that a majority of the top surface of theprotrusion electrode is covered by the conductive coating layer; andwherein a top surface of the conductive layer and a top surface of thesecond protection film form a smooth continuous transition at aninterface therebetween which is located on a sidewall of the protrusionelectrode.
 10. The semiconductor device of claim 9, wherein saidconductive coating layer is formed substantially conformally to the topsurface of the protrusion electrode.
 11. The semiconductor device ofclaim 9, wherein the only portion of the protrusion electrode that iscovered by the second protection film is an edge of the protrusionelectrode located proximate the boundary portion of the first protectionfilm.